Preparation of diaminomaleonitrile by chemical reduction of diiminosuccinonitrile

ABSTRACT

The process for the production of diaminomaleonitrile (HCN tetramer) by the reduction of diiminosuccinonitrile by certain chemical reducing agents, e.g., hydrogen sulfide or phenylhydrazine, is described.

Q United States Patent 1 i 3,714,222 Hartter [451 Jan. 30,1973

541 PREPARATION OF [58] Field of Search.... ..260/465.5, 465.5 R

DIAMINOMALEONITRILE BY v CHEMICAL REDUCTION OF [56] References Cited DIIMINOSUCCINONITRILE v UNITED STATES PATENTS [75] Inventor: Donald R. Hartter, Wilmington, j Y

Del. 3.55l,473 12/1970 Hillllel' .260/4655 R v 4 3,564,039 2 1971 Webster....; ..260/465.5 R [73] Assigneez E. I. du Pont de Nemours and Company wllmmgton Primary Examiner-Joseph P. Brust [22] Filed: Aug. 3, 1970 Altorney.lames HQ Ryan 211' App]. No.: 60,725

[57] ABSTRACT Related Apphcamm Data The process for the production of diaminomaleonitriie [63] Continuation-impart of Ser. No. 745,955 July 19, (HCN tetramer) by the. reduction of diiminosuc-. 1.963, 3,551,473 j cinonitriie by certain chemical reducing agents, e.g., g v v hydrogen sulfide or phenylhydrazine, is described. [52] US. Cl. ..-.....260/4 65.5 R [51"] Int. Cl ..C07c 121/20 8 Claims, No Drawings PREPARATION OF DIAMINOMALEONITRILE' BY CHEMICAL REDUCTION OF DIIMINOSUCCINONITRILE RELATED APPLICATION BACKGROUND OF THE INVENTION- 1. Field of the Invention This invention relates to, and has as its principal object provision of, the production of diaminomaleonitrile by the reaction of diiminosuccinonitrile with various chemical reducing agents.

2. Relationship to the Prior Art The prior art, e.g., The Chemistry of Imines, R. W. Layer, Chem. Rev. 63, 4895 (1963), gives many examples of the chemical reduction of N-substituted rmines. V v

The complete chemical reduction of an unsubstituted imine is reported by O. Cervinka [Collection. Czech. Chem. Commun. 30, ('7), 2484 (1965)], which shows reduction of C H ,,(C=NI-I)R, [R CH C,H C l-I a-naphthyl, o-tolyl and mesityl] with Li- Al(OR)H [R' ()menthyl and (+)bomyl].

None of the art shows chemical reduction of adiimines or bis-imines, and both Woodburn and Hoff man [.I. Org. Chem. 23, 263 (1958)] and Weidinger and Kranz [Ber. 97, 1599 (1963)] report unsuccessful attempts to reduce oxamidines [R -N1-I-alkyl] and oxaldiimidates [R=-O-alkyl]:

Webster US. Pat. No. 3,564,039 discloses the conversion of diiminosuccinonitrile to diaminomaleonitrile by a complex reaction with hydrogen cyanide plus a basic cyanide such as potassium cyanide.

My above-mentioned copending application claims the reduction of diiminosuccinonitrile to diaminomaleonitrile by means of hydrogen in the presence of a Group VIII transition metal hydrogenation catalyst.

DESCRIPTION OF THE INVENTION It has now been found that diiminosuccinonitrile can be reduced in good yield to diaminomaleonitrile by contact and reaction with certain chemical reducing agents in liquid phase. The reaction reduces the 2- imino groups, in effect by 1,4-addition, according to the following equation:

materials as diborane, anthracenebiimine, phosphine, triphenyltin hydride, lithium diethoxyaluminum hydride, and dimethyl borane.

As noted, the reaction takes place in liquid phase. The liquid phase may be provided by a wide variety of solvents or diluents that are described below. The principal requirements for the solvents are that they be liquid under the conditions employed and remain inert to the reactants and product. Since the solvents vary somewhat with the reducing agent, they are listed under the specific agents in the examples.

The reaction takes place at a temperature which varies somewhat with the reactants and, hence, is appropriately called an effective reducing temperature. For all the reducing agents, this range includes from 0 to +25 C. but may vary, even at both ends, according to the agent used. More specific ranges for the various types of reducing agents are as follows:

Broad Preferred Temperature Temperature Reductant Range C) Range C) Sulfhydryl 0 to p 0 to 50 NaBl-I. 20 to +100 -20' to +25 LiAlH, I 50 to +25 50 to +25 C,H,N,1I, 30 to +25 Pressure is not critical in the invention except to retain a liquid phase. Reaction time isnot critical.

' EMBODIMENTS OF THE INVENTION There follow some nonlimiting examples in which the process of the invention is'described in more detail. Temperatures are in degrees Celsius, and percentages are by weight, unless otherwise noted.

EXAMPLE I Hydrogen Sulfide Reduction of. Diiminosuccinonitrile A stream of hydrogen sulfide gas was bubbled through a slurry of 10.0 g (0.094 mole) of diiminosuccinonitrile in 100 ml of methylene chloride. The gas flow was continued for 30jrninutes at a rate such that the pot temperature did not go above 40 C. The reaction mixture was filtered to give 9.5 g of tan solid. Removal of the solvent gave another 0.6 g of solid. The 10.1 g of solid was washed with 100 ml of carbon disulfide to remove sulfur and 8.6 g (84 percent) of diaminomaleonitrile was obtained- This material was identified by its infrared spectrum which was identical with that of diaminomaleonitrile.

EXAMPLE 2- Hydrogen Sulfide Reduction of Diiminosuccinonitrile A slurry of 10.0 g (0.94 mole) of diiminosuccinonitrile in ml of methylene chloride was cooled to -30C and hydrogen sulfide gas was bubbled through the slurry for 10, minutes. No reaction ocan authentic sample of' diaminomaleonitrile as a red powder. Further recrystallization from water and treatment with decolorizing charcoal gave 7.1 g of white diaminomaleonitrile, identical to an authentic sample by infrared spectrum. The sulfur formed during the reaction did not dissolve in the water during recrystallization.

EXAMPLE 3 Thiophenol Reduction of Diiminosuccinonitrile A slurry of 2.0 g. of diiminosuccinonitrile, 4.0g. of thiophenol (phenyl mercaptan) and 100 ml. of methylene chloride was heated at reflux for 1 hour. The mixture was cooled and 1.0 g. of solid collected on a filter. Infrared analysis showed this to be a mixture of starting material and diaminomaleonitrile. Addition of petroleum ether to the filtrate precipitated 2.1 g. of a red solid that contained additional diaminomaleonitrile as evidenced by the infrared spectrum.

EXAMPLE 4 Ethanethiol Reduction'of Diiminosuccinonitrile fir r NH /C'C\ CrHsSH NC ON H,N NH, Hm N'H,

c=c NCCC CN N ON 0.115s S zHs A slurry containing 2.0 g. (0.019 mole) of diiminosuccinonitrile, 4 ml of ethanethiol and ml of methylene chloride was stirred at 26 C for 15 minutes and thenrefluxed for 30 minutes. The solution was cooled, 75 ml of petroleum ether was added. and the resulting mixture was filtered to give 0.9 g (43 percent) of diaminomaleonitrile. Upon standing, 1.0 g (23 percent) of the bis-thiol adduct crystallized as white needles.

Reduction of diiminosuccinonitrile can also be effected by other sulfhydryl compounds. These include arenethiols such as thiophenol, aand B- naphthalenethiol; alkanethiols such as methyl, ethyl, nand isopropyl and the butyl mercaptans; alkarenethiols such as 0-, m-, and p-cresols and the xylenethiols; and aralkanethiols such. as benzyl mercaptan, aand phenylethyl mercaptan, -y-phenylpropyl mercaptan.

' The lower alkyl mercaptans, i.e., mercaptans containing up to four carbon atoms, are preferred. These reductions can be carried out at temperatures ranging from 0 C. to 100 C., preferably at 0 C. to 50 C.

The solvent is not critical as long as it is nonreactive with the reductant or with the diiminosuccinonitrile.

convenient include methylene chloride, the dichloroethanes, tetrahydrofuran, dioxane, N,N-

dimethylformamide and dimethylsulfoxide. Benzene and toluene are also useful.

EXAMPLE 5 Sodium Borohydride Reduction of Diiminosuccinonitrile To a stirred solution of 3.0 g (0.028 mole) of diiminosuccinonitrile in 50 ml of methanol at 20 C was added 1.0 g of NaBl-l, in portions. The resulting solution was allowed'to warm to 25 C and poured into 200 ml of water. Approximately ml of solvent was removed on a rotary evaporator and the remaining aqueous solution was extracted with two 300-ml portions of ethyl acetate. The combined organic layers were'dried over MgSO and the solvent was removed to give 2.4 g (79 percent) of light tan diaminomaleonitrile.

Sodium borohydride reductions can be carried out in the lower, i.e., C -C alcohols, water, dioxane, tetrahydrofuran and diethylene glycol dimethyl ether (diglyme). This reduction is preferably carried out at -20 to 25 C. but can be runat higher temperatures thatrangeupto C.

Other alkali metal or alkaline earth metal borohydrides can be used in Example 5. These include beryllium, magnesium, cesium, lithium, sodium and potassium borohydrides. As sodium and potassium borohydrides are most readily available, they are preferred.

EXAMPLE 6 Lithium Aluminum 1 Hydride Reduction o f Diiminosuccinonitrile To a slurry of 1.52 g of LiAll-l, in 100 ml of dry ether was added 2.0 g (0.019 mole) of diiminosuccinonitrile in 200 ml of ether. After the addition was completed, the excess LiAll-l, was destroyed with water and 20 percent NaOl-l. The resulting dark colored solution was filtered'and the ether was removed to give 0.31 g (15 percent),of diaminomaleonitrile.

Lithium aluminum hydride reductions are usually carried out in ether solvents such as tetrahydrofuran, diethyl ether dioxane, 1,2-dimethoxyethane (glyme), 1,2-diethoxyethane, and diethylene glycol dimethyl ether (diglyme). This reduction is most conveniently carried out at ambient temperature but the temperature can range from 50 C. to +25 .C.

Any of the alkali metal or alkaline earth metal aluminum hydrides can be used in'place of thelithium aluminum hydrides of Example 6. The aluminum hydrides of the alkali metals are most readily available and of these, lithium, sodium, and potassium aluminum hydrides are preferred.

EXAMPLE 7 washed with ether and dried to give 3.3 g (61 percent) of diaminomaleonitrile.

The above reduction can also employ other hydrazines such as lower alkyl hydrazines, i.e., hydrazines having up to four carbon atoms, hydrazine and the closely related diimide EN NH, and these reductions can be carried out at -30 C. to 100 C. A preferred temperature range is --30' to 25 C.

As in other reductions, the solvent is not critical as long as it does not react with diiminosuccinonitrile or hydrazines. Suitable solvents include the lower aliphatic compounds containing up to and including five carbon atoms and selected from the class of alcohols, ethers, esters, halogen-substituted alkanes, nitriles and amides. Specific useful solvents include methanol, ethanol, nand isopropyl alcohol, the butyl and amyl alcohols, ethyl acetate, dioxane, tetrahydrofuran and glyme.

Since obvious modifications and equivalents in the invention will be evident to those skilled in the chemical arts, I propose to be bound solely by the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process of preparing diaminomaleonitrile which comprises reducing diiminosuccinonitrile in liquid phase by reaction, at an effective reducing temperature,

with a reducing agent of the group consisting of a. hydrogen sulfide and aliphatic and aromatic hydrocarbylsulfl'lydryl compounds containing up to 10 carbon atoms;

b. alkali metal and alkaline earth metal borohydrides;

c. alkali metal and alkaline earth metal aluminum hydrides; and i d. hydrazine, diimide and lower-alkyl hydrazines.

2. The process of claim 1 in which the liquid phase is provided by an inert diluent.

3. The process of claim 2 in which the temperature is about 0 to 50 C. and the reducing agentis hydrogen sulfide.

4. The process of claim 2 in which the temperature is about 0 to 50 C. and the reducing agent is thiophenol.

5. The process of claim 2 in which the temperature is about 0 to 50 C. and the reducing agent is ethanethiol.

6. The process of claim 2 in which the temperature is about 20 to 25 C. and the reducing agent is sodium borohydride.

7. The process of claim 2 in which thetemperature is about 50 to 25 C. and the reducing agent is lithium aluminum hydride.

8. The process of claim 2 in which the temperature is about -30 to C. and the reducing agent is a phenylhydrazine. 

1. The process of preparing diaminomaleonitrile which comprises reducing diiminosuccinonitrile in liquid phase by reaction, at an effective reducing temperature, with a reducing agent of the group consisting of a. hydrogen sulfide and aliphatic and aromatic hydrocarbylsulfhydryl compounds containing up to 10 carbon atoms; b. alkali metal and alkaline earth metal borohydrides; c. alkali metal and alkaline earth metal aluminum hydrides; and d. hydrazine, diimide and lower-alkyl hydrazines.
 2. The process of claim 1 in which the liquid phase is provided by an inert diluent.
 3. The process of claim 2 in which the temperature is about 0* to 50* C. and the reducing agent is hydrogen sulfide.
 4. The process of claim 2 in which the temperature is about 0* to 50* C. and the reducing agent is thiophenol.
 5. The process of claim 2 in which the temperature is about 0* to 50* C. and the reducing agent is ethanethiol.
 6. The process of claim 2 in which the temperature is about -20* to 25* C. and the reducing agent is sodium borohydride.
 7. The process of claim 2 in which the temperature is about -50* to 25* C. and the reducing agent is lithium aluminum hydride. 